Brush holder assembly for insulated housing



Dec. 6, 1966 G. E. MAFFEY, JR 3,290,524

BRUSH HOLDER ASSEMBLY FOR INSULATED HOUSING Filed March 25, 1964 2Sheets-Sheet l 4| 2 2| 45 l 43 33 GEORGE E. MAFFEY,JR.

ATTORNEY Dec. 6, 1966 MAFFEY, JR 3,290,524

BRUSH HOLDER ASSEMBLY FOR INSULATED HOUSING Filed March 25, 1964 2sheetswsheet 2 INVENTOR GEORGE E. MAFFEY, JR.

BY zgnna ATTORNEY United States Patent BRUSH HOLDER The presentinvention relates to a brush holder assembly for a motor housing madefrom an insulating material, and more particularly, to a brush holderassembly which is compatible with the design and manufacture of aninsulated electric tool.

It is an object of the present invention to provide a brush holderassembly which will fully comply with the various rigid safetyrequirements, such as the Continental Electrical Code, which governs theimportation and usage of electric tools in Europe.

It is another object of the present invention to provide a brush holderassembly having a terminal received Within a blind slotted recess orpocket formed within the insulated housing, the terminal beingelectrically connected to the brush, in combination with an insulatedmember secured to the housing and having an internal land portion whichsubstantially covers the opening in the recess so as to trap theterminal within the recess.

It is yet another object of the present invention to provide aninsulated member which serves a dual entrapment function: one, it trapsthe terminal within the recess and prevents the terminal or any portionthereof from com-ing out of the recess, should terminal breakage occur;and two, it traps the adjacent portion of the conductor against theinsulated housing and prevents the conductor from becoming loose andexposed, should a breakage occur between the conductor and its terminal.

It is a still further object of the present invention to provide aconductor having a resilient horse-shoe type of clip-on terminal whichis trapped within an internal recess or pocket formed within theinsulated housing; the clipon terminal is seated within an externalannular groove formed on a conductive brush holder insert that is inturn secured within a boss formed integrally within the insulatedhousing, the insert having a brush slidably guided therein andelectrically connected thereto, and the clip-on terminal serving theauxiliary function of helping to retain the insert within the housing inthe event that the brush holder insert becomes loose.

It is a still further object of the present invention to provide a brushholder assembly which may be fabricated and assembled into an insulatedportable electric tool with ease and convenience, one which iseconomical to produce, yet rugged and reliable for periods of extendedusage.

In accordance with the broad teachings of the present invention, thereis herein illustrated and described, an

electrical brush means for a housing made firorn an insulating material,the means comprising a brush which is slidably guided within theinsulated housing and a recess or pocket formed in the housingtransversely of the brush. The recess is substantially closed, but hasan opening through which it is accessible: and a conductor has aterminal means which is received through the opening in the recess andis electrically connected to the brush. A member, formed from aninsulating material, is secured to the housing; and the member has aninternal portion which substantially fits over the opening in the recessto trap the terminal therein. Additionally, and in a preferredembodiment, the insulating member pinches the portion of the conductor(which is adjacent to the terminal) against the insulated housing,thereby preventing an exposure of the conductor.

In accordance with the further teachings of the present invention, thereis herein illustrated and described, a brush holder assembly for ahousing made from an insulating material; the assembly comprises aconductive brush holder insert secured Within the housing, and a brushslidably guided within the insert and electrically connected thereto. Ablind slotted recess is formed in the housing, transverse to andcommunicating with the external surface of the insert. This recess,which is in the nature of a pocket, is substantially closed on threesides, but has an opening through which it is accessible. An externalgroove is formed on the conductive brush holder insert to communicatewith the recess. A conductor has a resilient substantially U-shapedclip-on terminal secured on its end; and the terminal is receivedthrough the opening of the recess and is seated Within the groove on thebrush holder insert to make an electrical connection with the insert,and through the insert, with the brush. An insulated means is thenprovided to trap the terminal in the recess, thereby preventing theterminal or any portion thereof from coming out of the recess and beingexposed, sh uld a terminal breakage occur.

In accordance with a first embodiment of the present invention,this'last-named insulated means to trap the terminal in the recesscomprises a window formed in the housing, the window facing the openingin the recess within which the terminal is received, and an insulatedcover plate seated in the window and secured to the housing; the coverplate has an internal land portion which substantially fits over theopening in the recess so as to trap the terminal therein.

While it is old in the art to removably secure a brush cover plate to amotor housing, nevertheless, the present invention transcends this priorart, not only in function, but also in structure. The purpose of thebrush cover plate of the prior art is merely to facilitate an inspectionof the brushes and the commutator. On the other hand, the presentinvention prov-ides a cover member which is molded from an insulatingmaterial and has an internal land portion which substantially encloses ablind slotted recess or pocket molded integrally within the housing, thelatter also being made of insulating material; and the insulated covermember thus serves the function of trapping a live terminal Within therecess, and preferably, of simultaneously trapping or pinching theadjacent portion of the live conductor against the insulated housing,thereby preventing exposure of the terminal, any portion of theterminal, or the conductor itself.

In accordance with another embodiment of the present invention, theinsulated means to trap the terminal in the recess comprises atransverse rear bridge, which is formed integrally with the insulatedhousing, and a longitudinally-split rear handle, which is also formed ofinsulating material, and is secured to the bridge. The handle has a pairof complementary mating halves, each of which is provided with anintegrally-formed internal land that encloses the opening in arespective recess so as to trap the terminal therein.

In accordance with a further concept of the present invention, theinsulated entrapment member is provided with a second internal portion,formed adjacent to its internal land portion, which pinches theterminals live conductor against a complementary ledge formed in theinsulated housing, thereby preventing an exposure of the conductorshould a failure occur between the conductor and its terminal.

These and other objects of the present invention will become apparentfrom a reading of the following specification, taken in conjunction withthe enclosed drawings, in which:

FIGURE 1 is a side elevation of a typical insulated portable electrictool with which the teachin the present invention may find partlcularutility;

FIGURE 2 is a transverse section, taken along the hnes 22 of FIGURE 1,enlarged over the scale of FIG 1, showing the manner in which a pair ofinternal lands on an insulated cover plate trap a pair of respectlveminals within their respective recesses in the insulated housing, andfurther showing the comp of one brush holder assembly in explodedrelationship;

FIGURE 3 is a detail section, taken along the lines 33 of FIGURE 2,showing the manner in which each terminal is trapped within itsrespective recess, and also showing the manner in which the adjacentportion of the conductor is Pinched or trapped between the insulatedmating portions of the housing;

FIGURE 4 is an exploded fragmentary perspective of the insulated coverplate and of the lower portion of the insulated housing, the latterhaving a window formed therein to receive the insulated cover plate;

FIGURE 4a is a partial perspective of the insulated cover plate, lookinginto the interior of the plate, showing the internal land which fitsover the opening in the recess to trap the terminal therein, and furthershowing the mounting bosses to secure the cover plate to the housinFIGURE 5 is another embodiment in which a longitudinally-split rearhandle is secured to a transverse bridge formed integrally with theinsulated motor housing, each handle half having an internal land whichtraps a respective terminal within its recess;

FIGURE 6 is a transverse section, taken along the lines 6-6 of FIGURE 5,and showing the manner in which the entrapment occurs; and

FIGURE 7. is a section taken along the lines 7-7 of FIGURE 6.

With reference to FIGURE 1, there is illustrated a portable electricsander 10 with which the teachings of the present invention may findparticular utility. The sander It) may be constructed as afully-insulated or all insulated electric tool; however, it will beappreciated by those skilled in the art that the teachings of thepresent invention are not necessarily confined to the particular toolshown, but rather are equally applicable to other tools, and indeed, toother types of electrical apparatus. With this in mind, and fororientation purposes, the overall sander 10 comprises a motor housing11; a gear case 12 secured forwardly of the motor housing; a main drivespindle 13; a rotating pad 14 driven by the spindle; the pad serving asthe support for an abrasive wheel, not shown, or for a buffing device orother tool; an end handle 15 secured rearwardly of the motor housing; anauxiliary side handle 15a (shown in end elevation) to assist in guidingand controlling the tool; an electric line cord 16 receivedby the endhandle; and a trigger switch 17 by means of which the sander isenergized.

With reference to FIGURE 2, it will .be appreciated that the motorhousing, and indeed the other housing components of the sander 10, aresuitably molded from an insulating material, such as a polyester resinhaving glass fibers embedded therein for structural purposes. The motorhousing 11 has a pair of integrally-molded bosses 18 which projectradially inwardly of the housing, and each of the bosses 18 has a bore19 and a counterbore 20 formed therein to communicate with the externalsurface of the housing. A substantially-cylindrical conductive brushholder insert 21 is secured within the bore 19 and has an annularshoulder 22 seated within the counterbore 20. The conductive insert 21has a series of longitudinal knurls 23, see FIGURE 2, formed on itsouter cylindrical surface by means of which the insert 21 ispress-fitted within the bore 1'9, and preferably, a suitable cement isalso used to retain the insert. The insert 21 has alongitudinally-formed through opening 24, which is preferablyrectangular in cross-section; and a carbon brush 25 is slidably guidedwithin the through opening 24 formed In the insert. The carbon brushes25 engage a Conventlonal drum-type commutator formed on a rotatingarmature (not shown for ease of illustration) and each brush 25 1sprovided with a necked-down rear portion 26, see FIG- URE 2, which seatsone end of a coil spring 27. The opposite end of the spring 27 is seatedagainst a conductive cap 28, and the cap 28 has a pair of ears 28a whichare slidably guided within the opening 24 in the conductive insert 21. Apair of flexible shunt wires 29, or other suitable means, are providedbetween the cap 28 and the brush 25 so as to electrically connect theconductive insert with the brush. The insert 21 has anexternally-threaded rear cylindrical portion 30 which receives aninsulated cap 31, and a protective metal ring 31a is cemented orotherwise secured to the housing to alleviate wear or accommodatescraping of the housing in the vicinity of the bosses.

With reference again to FIGURE 2, and with further reference to FIGURES3, 4, and 4a, a blind slotted recess 32 is formed in the boss 18,transversely of the bore 19 and intersecting the bore; and as shown moreclearly in FIGURE 3, this recess 32 is in the nature of an internalpocket which is substantially closed on three sides, but has an opening33 by means of which it is accessible. An external annular groove 34 isformed on the knurled cylindrical portion 23 of the insert 21, and thegroove 34, see FIGURE 2, is alined with the recess 32 when theconductive insert 21 is secured within the boss 18. A resilientsubstantially U-shaped clip-on terminal 35 is received through theopening 33 of the blind slotted recess 32 and is seated within theexternal annular groove 34 formed on the conductive 1br-ush holderinsert 21, thereby making electrical contact with the insert 21 (andthrough the insert 21, cap 28, and shunt 29) to the brush 25.Additionally, the terminal 35, in combination with the groove 34, servesthe auxiliary function of preventing axial movement of the brush holderinsert 21 out of the boss 28 in the housing. Each terminal 35 is securedto a live conductor or lead 36 by means of a conventional crimp-onconnector 37, and the conductors 36 come from the motor field coils (notshown) in a manner familiar to those skilled in the art. The electricline cord 16, moreover, has a pair of wires 38 and 39, see FIGURES 2 and4, which enter the motor housing through openings 40 and areinterconnected with the switch 17 and go to the motor field coils in aconventional manner.

Means are provided for trapping the terminals 35 within their respectiverecesses 32, and also, for pinching the adjacent portion of therespective conductors 36 against the insulated motor housing 11. In oneembodiment, the entrapment means, see FIGURES 2 and 4, includes a window41 formed integrally with the molded insulated housing 11 and facing theopenings 33 in the respective recesses 32. An insulated cover plate 42is seated in the window 41 and is secured to the housing; and the coverplate 42 has a pair of internal land portions 43, see FIGURES 3 and 4a,which fit over the respective openings 33, substantially enclosing therecesses 32, and trapping the respective terminals 35 therein. A firstpair of spaced-apart raised bosses 44, see FIGURE 4, are formed on eachboss 18 adjacent to one side of the opening 33 for the blind slottedrecess 32, and a complementary second pair of spacedapart raised bosses45, see FIGURE 4a, are formed in the insulated cover plate 42 adjacentto each land portion 43. When the cover plate 42 is seated in its window41, the complementary bosses 44 and 45 match with one another, seeFIGURE 2, and the plate 42 is secured to the housing 11 by means ofscrews 46 which pass through bores 47 in the second bosses 45 and arereceived in internally-threaded sleeves 48 anchored within the firstbosses 44.

With reference again to FIGURE 3, a ledge 49 is formed in the insulatedhousing 11 adjacent to each opening 33 in the respective recesses 32,and the insulated cover plate 42 has a complementary portion 50 formedadjacent to its internal land 43. As shown in the drawings, this portion50 is preferably formed as an extension of the land 43. When theinsulated cover plate 42 is secured to the insulated motor housing 11,the portion 36a of the live conductor 36 (adjacent to its terminal 35and crimp-on connector 37) is trapped, that is, pinched slightly betweenthe ledge 49 in the housing and the complementary portion 50 in thecover plate 42; and thus the insulated cover plate 42 serves a dualentrapment function: one, it traps the terminal 35 within the closedrecess 32 and prevents the terminal 35 (or any portion thereof) fromcoming out of the recess 32, should terminal breakage occur; and two, ittraps the adjacent portion 36a of the live conductor 36 and prevents theconductor 36 from becoming loose and exposed in the event that abreakage occurs between the conductor 36 and its terminal 35.

Another embodiment of the invention is illustrated in FIGURES 5, 6, and7; here, the invention is applied to an end handle fully-insulatedportable electric tool, such as a drill or screwdriver, The motorhousing, still designated by the numeral 11, is made of a suitableinsulating material and has an integrally-formed transverse rear bridgeportion 51 which is supported by integrally-formed struts 52.Mutually-alined conductive brush holder inserts 21 with brushes 25 aresecured within the bridge 51; The brushes 25 engage the commutator C onarmature shaft A. The brush holder inserts and related components aresubstantially identical to that which was described previously for thesander 10, and hence a further description has been omitted. The end orrear handle 53 is formed from a suitable insulating material and issplit longitudinally into a pair of complementary mating portions orhalves 53a and 53b. Each handle half is secured to the motor housing 11by means of screws 55 which pass through holes 55a in struts 52. Also,the handle halves 53a and 53b are secured to each other by screws 57.

As with the insulated cover plate 42 of the first embodiment, eachhandle portion has an internal land 43 which substantially fits over theopening 33 in each recess 32 to trap the terminal 35' therein, and also,an adjacent portion (not shown) which traps or pinches the conductor 36against the ledge 49 (see FIG. 7) formed in the insulated housing 11.The operation of this embodiment of the invention is thus identical tothe first embodiment, and it will be appreciated that the bridge 51 andsplit handle 53 serve the same entrapment function as the window 41 andcover plate 42.

Because of the resilient nature of the terminals 35 and the manner inwhich they are snapped in place, they remain in contact with theconductive insert 21 even after the cover plate 42 (or either handlehalf 53a or 53b in the other embodiment) is removed from the insulatedhousing 11; however, the terminals 35 may be easily snapped off of theinsert 21 by merely inserting a flat blade, such as a screwdriver, andlifting up on the connector 37.

Obviously, many modifications may be made without departing from thebasic spirit of the present invention; and accordingly, within the scopeof the appended claims, the invention may be practiced other than hasbeen specifically described.

I claim:

1. A brush holder assembly for a housing made from an insulatingmaterial, comprising, in combination:

(a) a conductive brush holder insert secured within the housing;

(b) a brush slidably guided within said insert and electricallyconnected thereto;

(c) a blind slotted recess formed in the housing transverse to, andcommunicating with, the external surface of said insert;

(d) said recess being substantially closed and having an opening throughwhich said recess is accessible;

(e) an external groove formed on said insert and communicating with.said recess;

(f) a conductor having a resilient substantially U- shaped clip-onterminal secured on its end, said terminal being received through saidopening of said recess and being seated within said groove on saidinsert; and

(g) insulated means to trap said terminal in said recess.

2. A brush holder assembly for a housing made from an insulatingmaterial, comprising, in combination:

(a) a conductive brush holder insert secured within the housing;

(b) a brush slidably guided within said insert and electricallyconnected thereto;

(c) a recess formed in the housing and communicating with said insert;

(d) said recess being substantially closed and having an opening throughwhich said recess is accessible;

(e) a conductor having a terminal secured thereto, said terminal beingreceived through said opening in said recess and engaging said insert;

(f) a window formed in the housing facing said recess;

and

(g) a cover plate made from an insulating material, seated in saidwindow, and secured to the housing;

(h) said plate having a portion substantially fitting over said openingin said recess to trap said terminal therein.

3. A brush holder assembly for a housing made from an insulatingmaterial, comprising, in combination:

(a) a transverse rear bridge formed integrally with the housing;

(b) a pair of mutually-alined conductive brush holder inserts securedwithin said bridge;

(c) a brush slidably guided within each of said inserts and electricallyconnected thereto;

(d) a pair of recesses formed in said bridge, one each communicatingwith a respective one of said inserts;

(e) said recesses being substantially closed and each having an openingthrough which said respective recess is accessible;

(f) a pair of conductors, each having a terminal secured on its end,said terminals being received in said respective recesses and engagingsaid respective inserts; and

(g) a longitudinally-split rear handle formed of insulating material andcomprising a pair of mating halves secured to said transverse rearbridge;

(h) each of said mating halves having an internal portion substantiallyfitting over said opening in said recess to trap said terminal therein.

4. A brush holder assembly for a housing made from an insulatingmaterial, wherein the housing is provided with an integrally-formedinwardly-directed boss which is closed on all sides, the improvementcomprising, in combination:

(a) a brush and means to slidably guide said brush within the bossformed in the housing;

(b) a slotted transverse recess formed in the boss,

intermediate the ends of the boss;

(c) said recess being substantially closed on three sides and having anopening through which said recess is accessible;

(d) a conductor having a terminal secured on its end, said terminalbeing received through said opening of said recess;

(e) means to electrically connect said terminal with said brush; and

(f) a member formed from an insulating material and secured within awindow in the housing;

(g) said member having a portion thereof substantially fitting over saidopening in said recess to trap said terminal therein.

5. A brush holder assembly for a housing made from an insulatingmaterial, comprising, in combination:

(a) a conductive brush holder insert secured Within the housing;

(b) a brush slidably guided Within the insert and electrically connectedthereto;

(c) a blind slotted recess formed in the housing transverse to, andcommunicating with, said insert;

((1) said recess being substantially closed and having an openingthrough which said recess is accessible; (e) a ledge formed in thehousing adjacent said opening in said recess;

(f) a conductor having a terminal secured on its end,

said terminal being received in said recess and engaging said insert;and

(g) a housing member made of an insulating material secured to thehousing;

(h) said member having a first portion substantially fitting over saidopening of said recess to trap said terminal therein; and

(i) said member further having a second portion, complementary with saidledge in the housing, to pinch therebetween the portion of saidconductor adjacent said terminal.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS4/1939 I Great Britain. 7/1951 Canada.

MILTON O. HIRSHFIELD, Primary Examiner.

D. F. DUGGAN, Assistant Examiner.

2. A BRUSH HOLDER ASSEMBLY FOR A HOUSING MADE FROM AN INSULATINGMATERIAL, COMPRISING, IN COMBINATION: (A) A CONDUCTIVE BRUSH HOLDERINSERT SECURED WITHIN THE HOUSING; (B) A BRUSH SLIDABLY GUIDED WITHINSAID INSERT AND ELECTRICALLY CONNECTED THERETO; (C) A RECESS FORMED INTHE HOUSING AND COMMUNICATING WITH SAID INSERT; (D) SAID RECESS BEINGSUBSTANTIALLY CLOSED AND HAVING AN OPENING THROUGH WHICH SAID RECESS ISACCESSIBLE; (E) A CONDUCTOR HAVING A TERMINAL SECURED THERETO, SAIDTERMINAL BEING RECEIVED THROUGH SAID OPENING IN SAID RECESS AND ENGAGINGSAID INSERT; (F) A WINDOW FORMED IN THE HOUSING FACING SAID RECESS; AND(G) A COVER PLATE MADE FROM AN INSULATING MATERIAL, SEATED IN SAIDWINDOW, AND SECURED TO THE HOUSING; (H) SAID PLATE HAVING A PORTIONSUBSTANTIALLY FITTING OVER SAID OPENING IN SAID RECESS TO TRAP SAIDTERMINAL THEREIN.